Telephone-exchange system.



PATBNITEDVOGT. 18,1904, J. L. MoQUARRIE. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JAN. 14, 1901- no MODEL.

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JAMES L. MCQUARRIE, or CHICAGO, ILLINOIS, AssIe'NoETo THE WEST- PatentedOctober is, 1,904.

PATENT OFFICE.

ERN- ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forining part of Letters Patent No. 772,900, dated October18, 1904.

' Application filed January 14, 1901. Serial No. 43,279. (No model.)

My invention relates to a telephone-exchange system, and moreparticularly to a system wherein a private branch telephoneexchange isprovided instead of a single instrument at a substation of a largeexchange. In large cltles It is not uncommon that abusinesshouse-requiring considerable tele-.

phone service to other parts of the city and also requiring alocaltelephone system for communicating between its departments will have alarge number of telephone instruexchange.

Inents distributed at various points throughout the premises, and all ofsaid instruments will be connected'with a private branchexchange-switchboard. One or more trunklines corresponding to ordinarysubscribers lines will then be provided between the private branchexchange and the main centralv office. With such a system when asubscriber of the large exchange desires communication with a particulardepartment of the business-house having the private exchange he willcall up the central oflice in the usual way and ask for connection withthe private The central-ofiEice operator will then [make connection withthe trunk-line leading to-the private exchange and applycalling-current.The private-exchange operator upon perceiving the signal thustransmitted will insert her answering-plug in the spring-jack of thetrunk line, at the same time connecting her telephone in circuit. Shewill then inquire of the calling subscriber the name of the person ordepartment wanted and having obtained this information will complete thedesired connection. When a person at one of the instruments of a privateexchange desires a connection with a subscriber of the large exchange,he will transmit his order to the private-exchange operator, who willconnect his instrument with the trunk-line leading to the centraloiiice, whereupon the central-office operator will answer the call inthe same manner as though it came from an ordinary substation. Theconnection of one of the private-exchange instruments with the maincentral office will not, of course, interfere with local communicationbetween any other two instruments of the private exchange.

In telephone systems of the character described it-is desirable that allthe substations of the private exchange should have substantially thesame equipment; but it is also desirable that through connection to thelarge city exchange should be permitted only to a certain few designatedinstruments. The object of this of course is to limit the use of thetrunk-lines strictly to business purposes, and so to reduce the numberof trunk-lines required. Where the common battery system is used, whilealocal source of current is provided at the private-exchange otfice forlocal connections it is desirable that for through connections to thecityvexchange the substation-transmitters should be operated bycurrentderived from the main-exchange battery-that is, the battery bridgedacross the central office operators plug circuitthesame as thoughconnection were had Irom the central oflice to an ordinary individualline.

The object of this invention is to provide a telephone system in whichthese results are attained.

In accordance with my invention an electromagnetic switch is connectedwith the private-exchan'ge-operators plug-circuit, which is brought intooperation by plugging into certain of the lines but not into others todisconnect or apply the local source of current for talking. Blockingmechanism is also provided for preventing telephonic communication, asby positively rendering the trunkline or other telephonic circuitinoperative when connection is made between the trunkline and asubstation which is not designed to be connected therewith.

My invention further contemplates improved means at the private-exchangeollice for controlling signals at the central ofiice of the largeexchange.

My invention is illustrated in the accompanying drawing, which is adiagram showing a trunk-line extending from acentral ofiice to aprivate-exchange ofiice and also showing two subscribers lines of theprivate exchange, together with the apparatus involved in connecting anddisconnecting lines, the system being constructed and equipped inaccordance with my invention.

The trunk-line, which extends in two limbs or line conductors 1 2 fromthe central ofiice A to the private-exchange office B, is provided atthe central oifice with the usual line-signal apparatus for indicating acall. Such signal apparatus is similar to that used on all subscriberslines of common-battery exchanges and does not require detaileddescription. At theprivatebranch-exchange office B the limbs 1 2 of thetrunk-line terminate in line-springs a 0/ of a spring-jack a. Aline-indicator or drop I) is connected in a terminal loop of thetrunk-line by way of two contacts, against which the line-springs a a?normally rest when no plug is inserted in the jack. Condenser b isincluded in the terminal loop containing the drop 5, so that the circuitof the central-office line-signal battery will not be closed throughsaid terminal loop. The continuity of the two conductors 1 2 iscontrolled by a blocking-relay 0. Said relay normally maintains thecontinuity of the trunk-line, but is adapted when excited to sever bothlimbs thereof. The magnet-winding of the relay 0 is included in aconductor 3, which extends from the test-ring or third contact-piece aof the spring-jack a to the pole d of the local-exchange battery (Z.

At the central oflice the trunk-line is connected with the usualterminal spring-jaclw and is equipped in the samemanner as an ordinarysubscribers line. I have. illustrated an operatorsplug-circuitat thecentral ofliee, adapted to make connection between the spring-jack ofthe trunk-line and the springjacks of other lines of the exchange. Thisplug-circuit is of the ordinary type and need not be particularlydescribed. It is equipped with the usual supervisory relays ff includedin the sleeve-strand thereof, and a battery f is connected in a bridgeof the plug circuit between the windings ot' a repeatingcoil. The relaysff control subsidiary signals ff", and when one of the plugs of theplugcircuit is inserted in the spring-jack c of the trunk-line thesupervisory relay corresponding to such plug is thus responsive to theflow of current from battery f through the trunkline. A calling-keyf isassociated with one of the plugs, said calling-key being adapted whendepressed to sever the cord-circuit and connect the terminalcontact-pieces of the calling-plug with the poles of an alternating generator. hen alternating calling-current is applied to the trunk-line tosignal the privateexchange ofiice, such current will traverse theterminal loop, which includes the condenser Z1 and trunk-line drop 6,whereby said drop will be caused to display its signal.

Two substation instruments G H of the private exchange are illustrated,said substation instruments being connected with correspondingspring-jacks r /1/ at the private-exchange ofiice. Thus the line-springs5 ol springjack r are connected with the line conductors leading tosubstation (i, and line-springs A h" of spring-jack /1/ are similarlyconnected with the line conductors leading to substation ll. Lineindicators or annunciators are provided for the substationtelephone-lines, each line having an annunciator connected in a bridgethereof, together with a source of current at the private-exchangeol'lice, and the springjacl; of each line is adapted when plugged intoto open the circuit of this bridge in a well-known manner. It isdesigned that station Gr shall be used not only to communicate withother stations of the private exchange, but also to be given throughconnection over the trunk-line with the city exchange, while substationH, on the other hand, is intended to be allowed only local service inthe private exchange. The equipment of the two stations (iand H and oftheir line apparatus at the central office is identical, with the singleexception that the spring-jack of the line ol station H is provided witha ring contact A, which is connected by a conductor 4: with the pole (Zof battery (I. The springjacl r has a similar ring contact; but nobattery connection therefor is provided.

The private-exchange operator is provided with a number of pairs ofplugs and their link conductors for making connections. ()ne of thesepairs of plugs with a cord-circuit therefor is illustrated in thedrawings. Each of the plugs 11 Z: is provided with threecontact-terminalsthe usual tip, ring, and sleeve contacts adapted toregister with corresponding contact portions of thespring-jacks. Thus,for example, when plug is inserted in spring-jack (6 the parts i f 1"register with and make contact with the parts a u" 1/" of saidspring-jack. The tips I A" of the plugs if .1', respectively, are unitedby the conductor 5 of the cord-circuit, and similarly the ring contacts1? A" are united by conductor (3, and contacts '11 K1 are united byconductor 7. The listening-key is adapted when depressed to connect theprivate-exchange-operatr rs telephone set in abridgebetween thecord-strands 5 6. The ringing-key m is adapted when depressed to severthe conductors 5 (S and connect the ends of said conductors which leadto the calling-plug Zr with the poles oi a calling-generator.

The local-exchange battery is connected in a bridge between theconductors 5 (3 of the conductor 5 through the'winding ',"and theplug-circuit, said bridgebeing Controlled by The windings 0 0 ofaretardaa relay n. tion-coil 0 are included in the bridge, one on eitherside of the battery 0?. The relay n is of comparatively'highresistanceand has two armatures, one of which is connected with theother is connected with conductor 6 through the winding 0 The armaturesnormally rest on back contacts, which are connected with the poles d drespectively, of the battery 4?.

When said armatures are attracted, they close against a pair of frontcontacts united by a conductor which includes a retardation-coil 5 1).Normally, then, the battery 0? is included in a bridge of thecord-circuit between the windings 0'0 of the retardation-coil 0, andwhen the relay n is excited the battery is cut off. and theretardation-coil p substituted therefor in the bridge-circuit Anelectromagnetic supervisory indicator is included in the circuit of thecord-strand 6 and is reponsive to current flowing therein. Saidindicator is adapted to display its'signal when inert.

' ductor 3. No circuit through the relay n is completed when both theplugs are inserted in local jacks, since the ring contacts of linesdesigned for private service only are connected withthe same pole, d ofthe battery, and the ring contacts of jacks g of lines permittedexchange service also have noconnection at all.

The relay 0, which is adapted when excited to sever the circuit ofthetrunk-line, constitutes a blocking device to prevent the use of thetrunk-line from substations similar to substation H. While circuit isalways com pleted through said relay cwhenever connection is made withthe trunk-line, yet when the trunk-line is connected with a substationoftype G the circuit through said relay includes the windings of thehigh-resistance relay n, so that suflicient current does not flow in thecircuit to excite relay 0," but when one of the plugs is inserted in thetrunk-line jack and the other is inserted in the jack of a station ofclass H a low-resistance circuit will be completed through the relay 0from the pole d of the battery cl to the ring a of jack a, contact 6 ofplug 2', conductor 7 of the plug-circuit to contact if of plug In,thenceto the ring contact if of the spring-jack it, and so by way ofconductor 4: to the other pole,

d of the battery. Current flowing in this circuit will excite the relay0 suificiently to cause the same to draw up its armatures, whereby thecircuit of the trunk-line will be broken and telephonic communicationprevented.

Whenever connection is made between the trunk-line and a station ofclass G, the relay n is excited by current flowing in the local circuit3 7 8, whereby said relay draws up its armatures and cuts off thebattery (Z from its bridge connection with the main conductors 5 6 ofthe plug-circuit, at thesame time substituting the retardation-coiltherefor. The substation-transmitter is then supplied with current, notfrom the battery cl, but from the main battery at the central ofiice ofthe cityexchange, the same as though the substation were an ordinarysubstation of that exchange. The maintenance of the bridge-circuit,including retardation-coils 0 and 9, during the coiinection with thetrunk-line serves to maintain acircuit for the supervisory relay fof thecentral-oflice-operators plug-circuit independent of the condition ofthe telephone-switch at the private exchange substation. Thecentraloffice'- operators supervisory lamp, therefore, is'not lighted toindicate a disconnection-signal until the connecting-plug at the privateexchange has been removed from the trunk-jack. If it were desired thatthe operator at the central oflice of the main exchange I those whichare permitted only private local 7 service. A blocking device 0 isprovided. for preventing telephonic communication between the cityexchange and substations of the private exchange which are not designedfor through connection, and said blocking device is actuated wheneverconnection is made between the trunk-line and such a substation. It isobvious that various means may be provided for blocking communicationother than by severing the trunk-line, and ldo not wish to be limited tothe precise means illustrated. When connections are made between localsubstations of the private branch exchange, current for exciting thesubstationrtransmitters is derived from the local battery (Z; but whenthrough connection is made from a sub. station to the central office Athe local battery d is cutoff and currentis derived directly from signaldevice of the A operators plug-circuit thus receives current as long asconnection is maintained with the trunk-line at the B switchboard and isindependent of the private-exchange-substation apparatus.

' Having thus described my invention, 1 claim as new, and desire tosecure by Letters Patent, the following:

1. In a telephone-exchange system, the combination with telephone linesof ditterent classes extending from substations to terminal spring-jacksat an exchange-switchboard, of a pair of connecting-plugs and linkconductors uniting them, for connecting lines together by plugging intothe spring jacks thereof, a trunk-line also having a terminal springjack at the exchange-switchboard, adapted to be plugged into by a plugof the pair aforesaid, a blocking device for preventing telephoniccommunication between a substation and the station of the trunk-line,and means, controlled by connection of the trunkline with any one of thelines of a certain class, for actuating said blocking device,substantially as described.

2. Inatelephone-exchange, the combination with a number oftelephone-lines of different classes extending from substations to anexchange-switchboard, of a telephone trunk-line extending from saidexchange-switchboard to a distant exchange, means for connecting any twoof said telephone-lines together and for connecting either of said lineswith the trunkline, and blocking mechanism, made operative in connectingsaid trunk-line with any one of the lines of a certain class, saidblocking mechanism being adapted to render inoperative the telephoniccircuit thereby established.

3. The combination with local telephonelines and a trunk-line, eachhaving switch-ten minals at an exchange, said trunk-line having a sourceof current in a bridge thereof at the distant station, of linkconductors for uniting any two lines at the said switch-terminals, alocal source of current in a bridge of said link conductors forsupplying current to the telephones of local lines united thereby, anelectromagnetic switch adapted when actuated to disconnect said localsource of current, and a local circuit for said electromagnetic switchclosed in connecting said link conductors to the trunk-line, wherebycurrentfor the local line is supplied from the distant trunk-linebattery during the connection of said local line with the trunk-line.

4:. The combination with a number of local telephone -lines havingcircuit controlling switches at the substations thereof andswitchterminals at an exchange office, of link conductors for unitingthe lines, a local source of current in a bridge of the link-conductorsfor supplying current to local lines united thereby, a special line alsohaving a switch-terminal at said exchange office, a battery and a signaldevice in the circuit of said special line at the distant stationtheretd, and a switch at the aforesaid exchange oiiice adapted todisconnect the local source of current from the link conductors andcomplete an independent bridgecircuit of low resistance across said linkconductors, whereby when a local line is united to said special linecurrent is derived from the battery in the special line, and the circuitthrough the signal device of said special line is maintained independentof the switch at the substation of the connected local line.

The combination with telephone-lines of different classes havingterminal switches atan exchange ofiice, and link conductors for unitinglines at the switch-terminals thereof, a local battery and circuitsconnecting the same in a bridge of the link conductors, anelectromagnetic switch controlling the connection of said local batteryin said bridge, a portion of a local circuit controlling saidelectronlagnel ic switch associated with the link conductors, andconductors associated with the terminal switches of a particular classof lines adapted to complete the local circuit controlling saidelectromagnetic switch when connection is made with such lines, wherebythe local battery is applied to the link conductors or not, according tothe type of line with which connection is made.

6. The combination with a telephone trunklinc extending between twoS\\il'cl]l) '):ll' ls A B, of a source of current in a bridge of theline' at the switchboard A, and a supervisory device connected in thecircuit, a spring-jack terminal for the line at the other switchboard B,a pair of plugs and a plug-circuit at the B switchboard for connectinglines together, a source of current and a retanlation-eoil normallyconnected in a bridge of the plug-circuit, and an electromagnetic switchactuated by connection of the plug-circuit with the trunk-line, adaptedto discmmect the source of current (J from the bridge of theplug-circuit and to complete said bridge independent of said source ofcurrent, substantially as described.

7. The combination with a telephone trunkline extending between twos\\'itchboards A 13, of other telephone-lines having spring-jackterminals at switchboard B, such other lines being divided into twoclasses, a plug-circuit connected with the trunk-line and having aplug-terminal adapted for insertion in the spring-jacks of the otherlines to make conncction therewith, an electromaguelie blocking device,a circuit incl uding a source of current, for said electromagneticblocking device, and switch-contacts associated with the spring-jacks ofall the lines of a particular class for establishing the circuit of saidblocking device when the plug is inserted in any spring-jack of saidclass, substantially as described.

8. In a telephone-excliange,the combination lished in connecting thespecial line with any of the lines of a particular class, wherebycommunication between the special line and the lines of such particularclass is prevented, substantially as set forth.

9. The combination with telephone-lines having terminal switches at anexchange office,' of link conductors for uniting the lines,

a special line having a battery and a signal operated thereby in itscircuit at the distant station, a source of current at the exchangeoffice, a switch adapted to connect said source of current in a bridgeof the link conductors, and a high-impedance bridge of said linkconductors independent of said source of current adapted to be completedby said switch in its alternative position whereby the signal of saidspecial line is controlled.

In witness whereof I hereunto subscribe my name this 28th day of July,AQD. 1900.

JAMES L. MCQUARRIE.

lVitnesses ELLA ED ER, ADELL HOGKETT.

